1. Field of the Invention
The present invention relates to low pressure warning devices, and more particularly pertains to embodiments of a new and improved low pressure warning device for use by scuba divers having both audible and visual indicators. Scuba divers are dependent upon a tank of compressed air to sustain respiration. The pressurized air in the tank is fed to a regulator to reduce the pressure to a level where it may be safely breathed by the diver. This pressure level is adjusted by the regulator depending on the current depth of the diver. The high pressure side of the regulator is conventionally monitored by a pressure gauge as an indication of the air supply remaining in the tank. A sufficient reserve must be maintained in the tank to allow the diver to ascend according to established rates to avoid rapid decompression which induces air embolism or the bends. This condition is also known as caisson disease, and is an extremely painful and life threatening illness. Divers must be constantly alert to the remaining air supply in the tank. A diver's attention is divided between the assigned task to be accomplished, or in the case or recreational divers, between their observations of aquatic marine life and photography, and the monitoring of the remaining air supply. The present invention is directed to a device for monitoring the remaining air supply and indicating a low air supply to the diver by both audible and visual signals.
2. Description of the Prior Art
Various types of indicating devices for monitoring pressure in containers are known in the prior art. A typical examples of such a device is to be found in U.S. Pat. No. 2,321,293, which issued to G. Hassler on June 8, 1943. This device utilizes a "U" shaped manometer and an associated scale to measure pressure in a container. U.S. Pat. No. 3,965,317, which issued to J. Gratzmuller on June 22, 1976, discloses a magnetically actuated switch for indicating the position of a piston in a fluid accumulator. U.S. Pat. No. 4,146,887, which issued to P. Magnante on Mar. 27, 1979, discloses a gas or vapor sensing alarm for use in an air purifying respirator. An exothermic sensor which can be fitted in the cartridge adapter or facepiece of the respirator monitors the heat evolved during adsorption of the gas or vapor into the sensor's adsorbent and triggers a visual or audible alarm. U.S. Pat. No. 4,191,952, which issued to P. Schreiber et al. on Mar. 4, 1980, discloses a device for monitoring relative flows in anesthesia gas and oxygen pipelines. A differential pressure sensing unit including diaphragms in both the oxygen and anesthesia pipelines triggers an alarm when the oxygen concentration drops below a predetermined limit value. U.S. Pat. No. 4,613,851, which issued to J. Hines on Sept. 23, 1986, discloses a device for monitoring pressure in pressurized carbon dioxide cylinders utilized in beverage dispensing systems. Magnetic reed switches mounted on the indicating needle and scale of a pressure gauge actuate staged alarms at a remote location dependent upon sensed pressure descent to first and second predetermined levels.
While the devices described above provide visual and audible indication of the pressure in a container at a remote location, none of these devices is suitable for use by a scuba diver, thus it can be appreciated that there is a continuing need for and interest in improvements in devices for monitoring and indicating low pressure conditions in scuba diving air tanks, and in this respect, the present invention adresses this need and interest.